The ultrasound system has become an important and popular diagnostic tool due to its non-invasive and non-destructive nature. Modern high-performance ultrasound imaging diagnostic systems and techniques are commonly used to produce two- or three-dimensional images of internal features of patients (target objects).
However, the ultrasound system suffers from inherent shortcomings of an ultrasound image such as a low signal-to-noise ratio and a limited field of view. Thus, the image registration of a CT (or MR) image onto the ultrasound image has been introduced in order to compensate for deficiencies of the ultrasound image. A sensor has been used to perform the image registration of a CT (or MR) image onto the ultrasound image. Researches have been introduced to calibrate the sensor to match coordinates of the CT image and coordinates of the sensor.
Conventionally, after outer markers are attached on a surface of a target object, a CT image and an ultrasound image for the target object with the markers are acquired. Thereafter, the calibration is carried out by using a relationship between coordinates of the markers in the CT and ultrasound image. That is, the outer markers should be attached to the surface of the target objects before obtaining the CT image and the ultrasound image and be maintained in the same position until completing the acquisition of the ultrasound image. Moreover, a sensor must sense the positions of the respective outer markers.
Further, the registration between the coordinate of the CT image and the coordinate of the sensor has been performed by manually inputting inner markers on the CT image. Thus, a user of the ultrasound system had to input the inner markers, which causes the registration between the coordinate of the CT image and the coordinate of the sensor to be wrong.